Problem with Winsock Control

I am only using machine names at the moment. I do not have anything defined in the hosts.sam file, because I am not using DNS. For the sake of simplicity, lets just say that I am making a chat program like winpopup. I am using the UDP protocol that is available with the winsock control.

VB Books Online come with some sample programs of how to make a simple Peer to Peer chat program with the winsock control. According to the examples, you should be able to just use machine names. I can't. Has anyone else tried this?

As mentioned by mcrider, you need to either use DNS, WINS or the HOSTS file. All this different method provides is a way to translate a name into an IP address. And for your home network, I would say DNS and WINS is an overkill.

Easiest way is to use the HOSTS file, create a HOSTS file, using the HOSTS.SAM as an example, put in your IP address and machine name separated by tabs. And put it in every PC that you got in your home.

Good luck,
Jim

Here's how I do it:

Private Type wsadata_type  ' returned by the WSAstartup call
    wVersion As Integer
    wHighVersion As Integer
    szDescription As String * 257
    szSystemStatus As String * 129
    iMaxSockets As Integer
    iMaxUdpDg As Integer
    lpVendorInfo As Long
End Type

Private Declare Function WSAstartup Lib "wsock32.dll" Alias "WSAStartup" _
        (ByVal wVersionRequired As Long, _
         lpWSAData As wsadata_type) _
         As Long
Private Declare Function WSACleanup Lib "wsock32.dll" () _
         As Long
Private Declare Function gethostbyname Lib "wsock32.dll" _
        (ByVal hostname As String) _
         As Long
Private Declare Function WSAGetLastError Lib "wsock32.dll" () _
         As Long
Private Declare Sub CopyMemoryToArray Lib "kernel32" Alias "RtlMoveMemory" _
        (destarray As Any, _
         ByVal src As Long, _
         ByVal bytes As Long)

Private Function GetIPAddress _
 (ByVal sComputerName As String) _
  As String
Dim wsadata As wsadata_type
Dim hostent(0 To 3) As Long
Dim IPptr(0) As Long
Dim IPaddr(0 To 3) As Byte
Dim nRet As Long
Dim hn As String * 128
Dim i As Integer
Dim s As String

    If WSAstartup(0&, wsadata) < 1& _
     Then Err.Raise WSAGetLastError(), "", _
     "Error getting IP Address."
    hn = sComputerName & Chr$(0)  ' null-terminate
    nRet = gethostbyname(hn)
    If nRet <> 0& Then
        ' returned address of a hostent structure
        ' copy structure from winsock memory
        Call CopyMemoryToArray(hostent(0), nRet, 16)
        ' copy pointer into IPptr variable
        Call CopyMemoryToArray(IPptr(0), hostent(3), 4)
        ' copy first IP address
        Call CopyMemoryToArray(IPaddr(0), IPptr(0), 4)
        For i = 0 To 3
            s = s & IPaddr(i)
            If i < 3 Then s = s & "."
        Next i
        GetIPAddress = s
    End If
    WSACleanup
End Function

I already do it this way, and so your answer doesn't really help.

What I'd really like to know is, can I get away with not assigning IP addresses? The documentation with the Winsock control gives me the impression that I shouldn't have to have IP addresses asssigned to a machine, but that instead I can just supply a machine name to the winsock control. It's a real nusaince having to have IP addresses, because if somone wants to use my program with a dial-up adapter, they have to assign an IP address to their machine, and then remove it so they can connect to the net. Any words of wisdom would be appreciated!

If you had a letter to send, but didn't know the address, and had knowone to ask (like our good friend DNS), how do you think the letter would be delivered ?

Even when you use a machine name, it has to be converted to an IP address, as someone said earlier, the easiest way is to use the hosts file, but you have to assign an IP address.  This shouldn't interupt your dial-up connection because (presumably) your assigning the IPS address to your network adaptor, not the dial-up adaptor.

In regard to woka's comments, I'd like to say one or two things.

* How do you think mailslots work? In WinPopup, you give a machine name, and it will deliver the message to the machine. Obviously the message gets sent to all computers, and the one with the appropriate name opens it. I had the idea the Winsock might use a similar method. Obviosuly I was wrong!

* You are right about an IP address not affecting dial-up because it is assigned to the network adapter, but what if my program is used on a machine where there is only a dial-up adapter? That is the problem.

I'll accept the answer here, because I have obviously run into a dead end. Thanks everyone.

Create two different dial-up profiles, one with an IP address (to use at home) and one without (for your ISP).  Then use the hosts table to enable the use of names.

That doesn't work. I've tried it.

If your program is running on a system with a dial-up only, then it has to dial into something to connect and send your information, right?

It will connect to a service provider and the service provider will assign a dynamic IP address.  With very few exceptions, you get a different IP address assigned every time you log on.

In this case you will have to have a server program running somewhere that is accessable to everyone using your program so your program can "announce" to the server that your program is running and what the dynamic IP address is.

When I do things like this, I use a web cgi program to keep track of connections... It goes like this in 7 simple steps...


1) Web CGI is always waiting for a connection.

2) User runs your program... it connects to the webserver on port 80 using the winsock DLL and announces its IP address to the server.  You can get your assigned IP address from the winsock DLL.

3) The Web CGI stores the announcement on the webserver and then broadcasts the IP address of everyone else that has announced themselves.

4) On a timer, your program optionally re-checks the webserver to see if new IP addresses have been announced.

5) You do your "program thing"

6) You announce to the webserver that your program is terminating, and it removes your IP address from it's broadcast list.

7) Your program terminates.



Simple huh?

It does work.  I'm doing it right now.  I have my ISP's profile, and one to dial into a PC running DUN Server.  Not all that easy to get it going I must admit, and I can't remember the steps to reproduce, but if you just keep changing things it works eventually !!

On the one with a hard coded IP, server types window has:

Log onto Network, Enable Software Compression and all 3 protocols checked.  All others are unchecked.  In TCP/IP settings, I've specified an IPS address, NOT specified a any DNS servers and have header compression and default gateway checked (what gateway ?!, still it works).

On my ISP profile, only Enable Software Compression and TCP/IP are checked in the server types window.  Under TCP/IP settings I have a server assigned IPS address, specified a primary and seconday DNS and have header compression and default gateway checked.

Both profiles use PPP.

Well, bubbles, after re-reading your original question, it seems to me that you have written a custom application that has to work only on your three local networked computers.  If that is the case, then why insist that the WinSock control has to work with a computer name?  Why not just set up a lookup table in your software with the three IP addresses, so you can refer to them by computer names or by any other designation you might wish to use?

Advice: Curt dismissals of genuine attempts to assist you as "not useful" don't inspire further offers of help.

Here's another option for you if you are only using 3 local systems. drop winsock completely and set up Network Neighborhood "Shared directories" on all 3 systems.

Then you can setup communications through the filesystem.
If for example you have 3 systems called Larry, Moe, and Curly you can set a shared directory on each system in C:\DATA.

Your program can use VB file open to communicate by opening the paths  "\\Larry\Data\com_file.txt", "\\Moe\Data\com_file.txt", "\\Curly\Data\com_file.txt".

Your program can communicate this way to your hearts content. If you are going to go this way, I suggest reading up on pipe files.

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In response to the comments:

RayDewey: My custom app is currently working with our three home computers. However, when it is completed I hope that it will be useful on any network, not just ours. I am not insisting that I must pass computer names to the Winsock control. In fact, I have had a lookup table like you described set up from the start. I was hoping I could forget about IP addresses and make my program easier to use and understand. I would like it so that I don't even have to setup any Network proocols either. Obivously, dreams are free. As for your advise on 'curt dissmissals'. While they may appear that way, maybe not everyone has as much time as you. I wouldn't take it personally. When I write things like that, I am usually in a hurry. My apologies if my comments appear unfriendly.

Mcrider: I have thought about that option, and also mailslots. However, I need security and I don't want my app to write to a disk at all - whether temp files or pipe files. If anyone knows of another method of peear to peer communication that is reasonably fast, secure, does not need to write to disk and will work over any network (dial-up or fixed) I'd be interested to hear what it is! I just figured Winsock does this best. Once again, I could be wrong.

Anyway. I appreaciate the way you guys stick at these questions. Thanks a lot.

Ok, One last thought, Add a registration server to your program. Your user's program would be configured with the name/IP address of the registration program.

The registration server would have a fixed IP Address.

PCs broadcast their IP addresses to the registration server, in return, the registration server would send the IP addresses of all the currently registered systems.

When the User wants to stop the program, the program contacts the registration server and tells it to remove it's IP address from the "currently active list", and tells all of the systems that it is connected to that it is leaving the group.